Filament winding apparatus



1967 D. s. RATHJE ETAL 3,304,705

FILAMENT WINDING APPARATUS 3 Sheets-Sheet 1 Filed Sept. 16, 1964 SignalGenerator Reference Comparison MetworK H h .K .T OS GDHR B 0 ST N H E eV .0 M N vlV KleinbF-ra.

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Feb. 21, 1967 5 RATHJE ETAL 3,304,705

FILAMENT WIND ING APPARATUS Filed Sept. 16, 1964 3 Sheets-Sheet 2 FormCompensating Comparison I Network Servo g}- d 44 \5 42 i 4o 38 ReferenceSignal Generator Fig. 20.

Herbert Baker, David S. Rclrhje,

INVENTORS.

(30love 8 Kleinberg,

ATTCRNEYS.

1967 D. s. RATHJE ETAL 3, ,705

FILAMENT WINDING APPARATUS 3 Sheets-Sheet 5 Filed Sept. 16, 1964 Fig.50.

WA Mondrel Drive Winding Head Assembl Form Compensohng I System AxialCorrection Servo Loop Gear Train Fig. 5b.

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United States hatent 3,304,705 FILAMENT WINDING APPARATUS David ShephardRathje, 10820 Melony Road, Culver City, Calif. 90230, and Herbert Baker,3218 Corinth Ave., Los Angeles, Calif. 90066 Filed Sept. 16, 1964, Ser.No. 396,903 12 Claims. (Cl. 5718) The present invention relates to afilament winding apparatus and more particularly to an apparatus forwinding a helical coil on a core.

Within the scope of the present invention, the term filament is to beconsidered to be composed of any material capable of sufiicientflexibility to be wound on a core or other form of any given crosssection. Although the invention has generally applicability, it isparticularly directed at apparatus for winding a wire helically about acore, the resulting product having utility as a wound electricalresistance element.

As taught in those patents, typical prior art coil winders include arotating wind-ing head, concentric and coaxial with a continuous form ormandrel. Rotatably mounted in the winding head is a concentricallymounted supply spool of filament which is to be wound about the mandrelor core. As shown in the prior art, filament is taken from a supplyspool, is directed to a mechanical tensioning arrangement, and iswrapped about a mandrel or form. The winding head rotates at relativelyhigh rotational velocities and the mandrel moves in the axial directionat a rate which is synchronized to the rotation of the winding head sothat the filament is uniformly coiled in a helix about the mandrel.

In prior art systems, the relatively simple friction or drag typetensioning systems utilized have not attempted to solve problems createdby wide variations in winding speeds, trapped wire, non-uniform spooldiameters, and variations in the free wire available from the spool. Asthe filament is unwound from the sup-ply coil, the filament being takenfrom the reel moves axially which introduces changes or variations intension due to the inertia of the spool which is otherwise tree torotate.

Various mechanical linkage systems have been proposed to maintainfilament tension but, at high speeds, the mechanical tolerances andspeeds of response are such that the efiiciency of the linkage system isnot much better than that of drag tension systems.

Another problem encountered in using prior art coil winding systems,especially in winding of extremely fine gauge wires on heavier gaugemandrels to produce precision resistance elements, has been thevariation in turnto-turn spacing when wire is being wound at speedsapproaching 5000 rpm. Although the problem is not severe with 'fairlyheavy gauge wire filaments, diameters of approximately 1 mil or greater,it has been found desirable to attempt to maintain a relatively uniformspacing between adjacent turns to prevent shorting of adjacent turns andto maintain constant resistance per unit length. When very fine wires,less than 1%. mils, are being wound on a mandrel at Winding speeds ofthe order of 5000 r.p.rn., it has been discovered, that when frictiontensioning systems are used, wide variations are noted in theturn-to-turn spacings. Consequently, spacings less than one mil aredifficult, if not impossible to achieve uniformly on a long term basis.It is suspected that the cause of variation in turn-to-turn spacing maybe due to the resiliency of the filament wire being wound and the effectof changes in tension upon the point at which the wire contacts themandrel. At relatively low tensions, the wire may extend in asubstantial arc with a relatively large loop of wire disposed betweenthe friction head and the point of wrap. Alternatively, when tension isrelatively high, there is virtually no slack in the filament wire andthe point of wrap is, for all intents and purposes, at a point tangentto a straight line from the tensioning mechanism to the mandrel. If thelateral motion of the mandrel is maintained at a constant speed, thenchanges in tension will change the point of attachment and,consequently, the turn-to-turn spacing will vary widely.

In the past, therefore, to avoid wide variations in filament tension, tomaintain relatively constant turn-to-turn spacing, to attempt to controlthe linear resistivity of the wound mandrel, and to attempt to overcomethe effects of the inertia of the supply spool, filament wires of lessthan l-mil were wound at winding speeds substantially less than 5000r.p..m., and the speed varied almost directly with the wire size,smaller diameter wires being wound at slower speeds.

Further problems in maintaining filament tension are encountered when afilament is to be wound about a form of non-circular cross section. Theconventional approach to this problem has been to hold the supply spoolstationary and rotate the form, while advancing the form or spoollaterally. In designing apparatus which does not rotate the form, butwhich advances it laterally only, revolving the winding head about theform, the problem or" a point of wrap of non-constant length createsgreat variations in tension during each revolution of the winding head.Further, if such a non-uniform winding form also has variations in crosssection that are cyclical with respect to lateral motion of the form,then still further changes in tension are produced during the windingoperation.

It has also been the practice in certain prior art winding machines,that the supply spool be arranged to run freely in the direction ofwinding head rotation at a rotational velocity slightly greater thanthat of the winding head. To arrange the supply spool oppositely sothat, by rotation of the winding head, wire is taken from the spool, thespool would have to be driven substantially at the rotational velocityof the winding head to prevent accumulating a loop of wire with eachrotation of the winding head.

In other prior art machines, the supply spool is permitted to run freelyand tension is regulated by frictional drag members in the idler pulleysthat direct wire travel from the take-off spool to the core or mandrel.Such an arrangement would, over a period of time, introduce changes inwire tension since, at start up, the inertia of the supply spool acts asa dead weight on the wire, resulting in a relatively high degree oftension until the spool came up to speed. The tension then decreasesuntil only the frictional drag of the rotating spool results in tensionin the wire. However, as the mass of the supply spool decreases with theutilization of wire, the spool may tend to speed up and equal orover-run the velocity of the winding head, resulting either in acompletely slack supply or substantially reduced tension in the Wire' tothe tensioning mechanism.

Although the preferred embodiment of the present invention is shown anddescribed in conjunction with a machine :for coiling resistance wire ina helix on a mandrel, it is clear that the present invention has utilityin other machines which are adapted to wind one or more filaments on acore of any sort. Further, although the preferred embodiment has beenshown with a supply spool concentric with the winding head, it is wellwithin the scope of the present invention to have one or more supplyspools eccentrically, mounted and driven accordingly. Certainly, suchwould be the case in machines wherein filaments are wound upon a formwhose diameter exceeds the inner diameter of the core of a supply spool.

In order to maintain a constant tension in a filament being wound, andto overcome the problems inherent in prior art mechanisms, the presentinvention provides a servo-controlled differential mechanism for drivingthe supply spool at a rotational velocity slightly greater than that ofthe winding head in order to feed wire, and yet at a controlled ratesuch that the tension in the wire is held constant at some desired,predetermined value. This is accomplished by interposing a tensionsensing member in the path of filament travel which, in conjunction witha transducer, can signal the deflection of the interposed member and thetension ,in the winding proportional thereto. The tension sensing memberalso introduces a slight buffering effect in that it will yield undersudden increases in tension, shortening the wire travel path.

A reference voltage is generated which is carefully calibrated toprovide signals corresponding to the signals producedby the sensingmember throughout the desired range of tension. An error amplifiercompares the reference signal and the sensing signal and generates anerror signal to a servo amplifier which in turn controls a servo motorthrough a gear train into one input of a mechanical differential. Thesecond input to the differential is provided by the rotation of thewinding head and the two motions are additively combined in thedifferential output which in turn drives the spool.

When tension in the supply wire exceeds the desired amount, the signalgenerated by the interposed member is greater than the reference signaland accordingly the error signal to the servo system energizes the servomotor in a sense that would cause increase in the rotational velocity ofthe supply spool. This rotational motion is applied to one of the inputsof the differential where it is additively combined with the rotationapplied from the winding head drive and the combined, increased rotationis applied to the supply spool to increase its rotational velocityrelative to that of the winding head, thereby decreasing tension in thewire or filament.

In an embodiment of the present invention, provision is made to Windfilaments, on non-uniform cores of other than circular cross section. Insuch a device, it will be readily appreciated that the point of wrapchanges rapidly with the rotation of the winding head, and accordingly,the demand for the filament changes rapidly during a single revolution,which would require a response beyond the frequency range of the servosystem. Accordingly, a correction generator which, in one embodiment,includes a cam and follower arrangement is provided to generate acompensating motion for any particular elongated form of non-constantcross section in the axial direction.

A mechanical difierential is provided which now receives one of itsinputs from the correction generator and the other from the servo motorand gear train which corrects filament tension, as above. The output ofthis differential which receives an input from the Winding head and theadditive sum of the motions is applied through the output to drive thesupply spool.

In yet another embodiment, if a filament is to be wound upon a corehaving a changing cross section in the axial direction, this too, can becompensated for, if the change is cyclical and repeatable. In thisembodiment, a me-' chanical differential is provided receiving one inputfrom the correcting device which may also be a cam and followerarrangement, and a second input from the apparatus driving the core ormandrel in the axial direction. This mechanical differential output canthen be applied as an input to a differential whose other input issupplied by the servo system or, if it is a form of non-uniform crosssection which is also varying in the axial direction, then thecorrecting differential for axial length of the mandrel can be includedin the differential train so that the ultimate drive to the suppy spoolcan be the sum of all of the applied inputs.

Accordingly, it is an object of the present invention to provide animproved apparatus for maintaining tension in a filament windingassembly.

It is further an object of the present invention to provide an improvedapparatus that is responsive to correct for rapid changes in tension ina high speed filament winding apparatus.

:It is yet another object of the invention to provide a tensioningsystem for a high speed filament win-ding apparatus which includes aresilient member, interposed in the path of filament travel, that isconnected in a servo loop to maintain a predetermined tension.

It is an additional object of the invention to provide an improvedtensioning apparatus which includes a servo controlled diiferentialmechanism for applying small changes in rotational velocity to thesupply spool of a high speed filament winding apparatus.

It is yet a further object of invention to provide a filament tensioningsystem in which a transducer interposed in the path of filament travelis connected to control a servo loop includinga differential mechanismfor driving the supply spool in a sense to compensate for tensionchanges.

It is yet an additional object of invention of provide a filamenttensioning apparatus in a high speed coil winder which compensates,through a differential mechanism, not only for changes in filamenttension, but for predictable irregularities in the form of mandrel aboutwhich the filament is being wound.

It is yet another object of invention to provide improved apparatus forwinding extremely fine filaments at winding speeds of over 5,000 turnsper minute while maintaining turn-to-turn spacings of less than thediameter of the filament being wound.

It is yet an additional object of invention to provide in a high speedcoil winding apparatus for winding precision resistive elements, a wiretensioning system for correcting and driving the wire supply spool in asense to maintain the tension at a predetermined value.

It is yet an additional object of the invention to provide a high speedcoil winding apparatus for producing precision potentiometer coreshaving an extremely sensitive tensioning system for driving a filamentsupply spool at rotational velocities slightly greater than that of thewinding head, yet controlled to maintain tension at a predeterminedvalue.

It is still a further object of invention to provide a high speed coilwinding system having a tensioning system including a transducerresiliently mounted in the path of resistance wire travel and connectedin a servo loop driving a differential core correcting the rotationalvelocity of the supply spool to maintain tension in the resistance Wireat a predetermined value at all times.

The novel features which are believed to be characteristic, both as toorganization and method of operation, together with further objects andadvantages thereof, will be better understood from the followingdescription considered in connection with the accompanying drawings inwhich several embodiments of the invention are illustrated by way ofexample. It is to be expressly understood, however, that the drawingsare for the purpose of illustration, and description only, and are notintended as a definition of the limits of the invention.

FIG. 1 is a functional block diagram of one embodiment of a filamenttensioning system according to the present invention;

FIG. 2 includes FIGS. 2a and 2b in which FIG. 2a is a diagram partiallyin block form, of an alternative embodiment of the tensioning system ofthe present invention modified for use in winding coils uponnon-circular forms such as shown. in FIG. 2b.

FIG. 3 includes FIG. 3a and FIG. 3b in which FIG. 3a is a partial block,partial schematic diagram of still another embodiment of the system ofthe present invention, and FIG. 3b is a partial side view of analternative non-uniform mandrel or form about which the filament iswrapped;

FIG. 4 is a side view of a cantilever beam assembly for determiningfilament tension according to the present invention; and

LII

FIG. is a front view of the apparatus of FIG. 4 taken along the line 55in the direction of the appended arrows.

Turning first to FIG. 1, there is shown partially in block and partiallyin schematic form, a portion of a winding system that includes atensioning system according to the present invention.

As illustrated, the tensioning system 10 includes a Winding headassembly 12, a servo loop 14 and a supply spool drive train 16.

A form or mandrel 18, about which a wire or filament 20 is Wrapped, is,in a preferred embodiment, coaxial with a winding head 22. The windinghead 22 is driven by a high speed motor through suitable transmissionassemblies for example, in a manner shown in U.S. Patent No. 2,334,880,and is, in one embodiment adapted to rotate at speeds in excess of 5000rpm. The filament 20 is taken from a supply spool 24 which, in thisembodiment is concentric and coaxial with the mandrel 18 and is alsoconcentric with the winding head 22. A supply spool drive shaft 26 isjournaled in the winding head and provides means for independentlyrotating the supply spool 24 with respect to the Winding head 22.

Fliament 20 is taken from the supply spool 24 and is passed over anidler 28 which is supported by a transducer 30 that is adapted to detectand signal tension in the filament 20. In a preferred embodiment, thetransducer 30 includes a cantilever beam 32 which introduces a rightangle in the path of filament travel, and a second idler 34 whichintroduces a second right angle into the path of filament 20 travel,from whence it is applied to the mandrel 18.

The transducer 30 is electrically connected to a power supply andsignals from the transducer 30 proportional to and representative offilament tension are provided through a slip ring brush assembly 36.

The slip ring brush assembly 36 is electrically connected to the servoloop 14 which includes, as shown in block form, a reference signalgenerator 38 and a comparison network 40. In one embodiment thereference signal generator includes a precision potentiometer or othervariable resistance means which is connected to :the power supply. Thereference signal genera-tor 38 is designed to produce a signalequivalent to that provided by the transducer 30 under different loadsand which will be proportional to and representative of desired tension.Thus, 'by a suitable adjustment, the reference signal genera-tor 38 canbe calibrated directly in filament tension by applying measured tensionsto the fila ment and comparing .the output of the transducer 30 withthat of the reference signal generator 38. After calibration, desiredtension settings can be made directly to the reference signal generator38. The output of the reference signal generator 38 is applied to acomparison circuit 40, the other input to which is provided from slipring and brush assembly 36 and an error signal will be generated havinga magnitude and polarity corresponding to and representative of thedifference between actual tension in the filament 20, as measured by thetransducer 30, and the desired tension in the filament 20 as signalledby the reference signal generator 38. In one embodiment, positive errorsignals indicated greater than desired tension and negative errorsignals' indicated less .than desired tension.

The output of comparator 40 is applied to a servo amplifier 42 whoseoutput is applied to a servo motor 44. Servo motor 44 is a part of thesupply spool drive train 16. The mechanical, rotational output of servomotor 44 is applied through a gear train 46, including appropriatereduction gears. The output of the gear train 46, is applied to oneinput of a two-input mechanical differential 48, whose output is made tobe the sum of the applied inputs. The second input is provided from thewinding head 22 and the output of the differential represents the sum ofthe applied rotations.

Any type of differential driving mechanism may be employed that willalgebraically add the rotation of the servo motor gear train 44, 46, tothe rotation of the winding head 22, and the output is applied to thesupply spool drive shaft 26 to rotate the supply spool 24.

In operation, the apparatus is arranged so that the core or mandrel 18is applied to pass through the winding head in the axial direction at arelatively slow rate of feed. The winding head is driven to Wrap thefilament 20 in a helix about the mandrel 18. The path of filament 20travel extends from the point of Wrap on the mandrel 18 to the secondidler 34, the first idler 28 and over the cantiliver beam 32 to thepoint of take-off from the supply spool 24.

As the winding head 22 rotates, the rotational motion is applied to thesecond input of the mechanical differential 48. Assuming that nocorrection for tension is present, then that rotational motion isdirectly applied to the supply spool drive shaft 26 and the supply spoolwill be driven at substantially the same rotational velocity as thewinding head 22.

As filament 20 is wound about the mandrel 18, additional filament mustbe drawn from the supply spool 24 and, to the extent that a pull ortension is applied to the filament 20, the cantilever beam 32 will bedeflected as the supply spool resists any increase in rotationalvelocity over that of the winding head 22. Accordingly, the tension willbuild up in the filament and a signal from the transducer 30 will beapplied through the brush slip ring assembly 36 to the comparator 40which then generates an error signal of a polarity indicating anincrease in tension.

This error signal is applied to the servo amplifier 42 where it isamplified and applied to the servo mot-or 44 and its connected geartrain 46. The signal to the servo motor 44 and gear train 46 generates arotation in the direction of the winding head motion and this is thenadded to the first input of the mechanical differential 48.

The output of differential 48 then is the sum of the applied rotationsand the drive to the supply spool is then increased, speeding up thesupply spool 24.

So long as the tension in the filament 20 is the desired tension, thenthe output of the transducer 30, when compared to the output of thereference signal generator 38, in the comparator 40 will provide a smalloffsetting, or zero error signal which is applied through the servosystem to drive thesupply spool at a slightly greater velocity than thewinding head, to permit the filament to unreel without setting upundesired oscillations in the servo part of the system as the result ofovershoot in the correction.

If the supply spool 24 speeds up and the tension decreases, thedesiredtension signal from the reference signal generator 38 will be thegreater and the error signal will be of the opposite polarity. Thiserror signal when amplified and applied to the servo 46, tends to applya rotational input to the differential which is effectively subtractedfrom the winding head input tending to slow the supply spool 24 andthereby causing an increase in filament tension.

An alternative embodiment is shown in FIG. 2 which includes, in additionto the systems elements of FIG. 1, a form compensating system 50 topermit uniform tension on a filament that is being wrapped about anon-uniform form or mandrel. As shown in FIG. 2a, a rectangular bar 52is shown as the mandrel, and as can be seen in FIG. 2b, this shapeimposes a non-uniform demand upon the filament supply system, which, ifuncorrected, could result in wide variations in filament tension.

To help compensate for this variation in demand, a second mechanicaldifferential 54 is provided. The second mechanical differential 54 isconnected to receive one output from, as shown here, a cam follower unit56 that includes a slotted cam 58 and a crank type follower 60, which issuitable for winding speeds of up to 2000 r.p.m. For higher windingspeeds, a more sophisticated compensating system would be required suchas a gear train utilizing elliptical gears, of perhaps a hydraulic servosystem. The cam 58 is driven in synchronism with the winding head 22 andprovides a first input to the second mechanical differential 54. Thesecond input to the differential 54 originates from the servo motor 44and the gear train 46 as described in connection with FIG. 1, above. Theoutput of the second differential 54 is applied to one of the inputs ofthe first differential 48. The second input to the differential 48 comesfrom the winding head 22, and the combined output of the firstdifferential 48, is as before applied to the supply spool drive shaft26, so that in this embodiment, the rotation of the supply spool 24 isthe resulting summation of the rotational motion of the winding head 22and the corrections applied by the servo motor 44 and the gear train 46,and by the cam follower unit 56 of the compensating system 50.

In FIG. 3a, there is illustrated still another alternative embodimentfor maintaining a constant uniform tension on a filament which is to beWound upon a non-uniform core 62 of cyclically varying cross section.For example, FIG. 3b illustrates a portion of such a form 62 which inthis case is a rectangular continuous strip having a repeating saw toothpattern 64.

In this embodiment, a third mechanical differential 66 is provided whichreceives as one mechanical input, the output of a second compensating oraxial correction system 68 which is driven by a connection to the formor mandrel drive'mechanism which advances the mandrel through thewinding head assembly 12. Typical mandrel drives are shown in Marlowe,above. The compensating or axial correction system 68 may besubstantially similar to the form compensating system 50, and mayinclude a cam and follower arrangement.

The third differential 66 has its second input connected to the outputof the form compensating system 50. The output of the third differential66 now serves as the input to the second differential 54 and theremaining elements of the system are connected as in FIG. 2a.

The series of differentials can be considered, generally, as one form ofcompensating and correcting means which is wholly mechanical. Otherembodiments would include combinations of electrical and mechanicalelements, even all-electrical embodiments can be devised by one skilledin the art.

A suitable transducer element 30 is shown in FIGS. 4 and 5 which are aside and front view, respectively, of the cantilever beam member 32 ofFIG. 1. As shown in more detail, the cantilever beam 32 has affixed toone face, a signalling element which, in a preferred embodiment is astrain sensitive gauge 70, bonded to the body of the cantilever beam 32.Suitable electrical leads 72, 74 connect through the slip ring brushassembly 36, to a suitable power supply and balancing network (notshown) so that the cantilever beam member 32 can provide signals whichare proportional to the deflection of the beam. As will be clearly seen,the cantilever beam deflection is entirely due to tension in thefilament 20 as it makes the turn from the supply spool 24 to the secondidler 34.

It will be apparent to those skilled in the art that the particularcircuits comprising the reference signal generator 38, the comparator40, the servo amplifier 42 and servo motor 44 are well known in art andaccordingly, no particular circuits have been set forth. Similarly, thedetails of mechanical gear trains 46 and mechanical differentials areequally well known and will not be discussed in detail herein. Further,the selection of a particular cam follower combination to compensate fornonuniform cross sections or for a cyclically varying form are wellWithin the skill of the artisan and need not be discussed in detailherein other than to state that such mechanical compensating systems areeasily provided without the exercise of inventive skills.

It is also within the skill of the art to provide suitable electricalcompensating circuits whose outputs, when electrically combined withthat of the servo amplifier 42, would compensate for variations in theshape of the mandrel and for cyclical variations in the mandrel as afunction of axial position of the mandrel. In such an embodiment, only asingle mechanical differential need be provided, one input of whichwould be supplied by the servo motor and gear train, and other input ofwhich would be the winding head. The output of the differential would beapplied to drive the supply spool.

Broadly, in operation, as the filament is wound about the form ormandrel, any tensions introduced by the movement of the point of wrap onthe form can either be mechanically or electrically compensated andcorrected for, as a function of some combination of winding headrotation and mandrel movement.

The tension in the filament resulting from the unwinding of the filamentfrom the supply spool is compensated for by a servo loop whichcontinually senses the tension in the filament and compares the tension,represented by a signal from a reference signal generator. An errorsignal is then produced which, when applied to a servo amplifier-servomotor combination and gear train through a mechanical differential,continuously corrects the supply spool drive to maintain the filamenttension at the predesired value. Any tensions introduced bynonuniformities in the mandrel or movement of the point of wrap on theform can be compensated for either electrically or mechanically andthese compensations can be superimposed on the corrections alreadygenerated.

Although the apparatus as described and shown is useful in the windingof resistance wire in a helix to form a resistive element, similarapparatus could be used, using other types of filaments and cores forthe winding of musical instrument strings. Also, in embodiments whereinthe form or mandrel is of an unusually large cross section, larger thanthe inner diameter of a filament supply spool, the filament supply spoolcould be mounted eccentrically on the winding head. The drive to thesupply spool would be reconnected accordingly, and might eliminate theneed for the mechanical differential, and the servo motor gear traincould be mounted on the winding head to drive the supply spool directly.In this embodiment, if non-uniform cross section mandrels are used,electrical compensation would be preferable. In this case, theelectrical output is applied directly to the servo loop of the supplyspool.

Thus, there has been shown a novel system for maintaining apredetermined tension on a filament on a winding apparatus havingseveral embodiments. The tension on the filament is sensed and, throughsuitable transducers, a signal is generated which can be used to correctfor variations from desired tension by varying the rotational velocityof the filament supply spool through a suitable servo loop including anerror generator, an error amplifier, a servo motor, gear train andmechanical differential.

What is claimed as new is:

l1. In a high speed winding apparatus for winding a filament about acore, the apparatus having a winding head rotatable about the core, afilament supply spool rotatably mounted on the winding head and meansfor rotating the winding head at relatively high rotational velocitiesto form a coil about the core, apparatus for maintaining a predeterminedtension in the filament comprising:

tension sensing means coupled to the winding head and interposed in thepath of filament travel and adapted to provide a signal proportional toand representative of the tension in the filament being wound on thecore;

tension reference means adapted to provide a signal proportional to andrepresentative of a desired, predetermined tension in the filament;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal proportional toand representative of a deviation in measured tension from desiredtension; and

servo correcting means connected to said error sensing means andoperable in response to said error signal for changing the rotationalvelocity of the supply spool during rotation of the winding head tomodify the filament tension in accordance with said error signal,whereby said servo means affects the rotational velocity of the supplyspool to change the filament tension in a sense tending to decrease themagnitude of the error signal.

2. In a high speed coil winding apparatus for winding wire about amandrel, the apparatus having a rotatable winding head coaxial with themandrel, a wire supp-1y spoolrotatably mounted on the winding head andmeans for rotating the winding head at relatively high rotationalvelocities for winding a helical coil on the mandrel, apparatus formaintaining a predetermined tension in the wire comprising:

tension sensing means coupled to the winding head and interposed in thepath of wire travel and adapted to provide a signal proportional to andrepresentative of the tension in the wire being wound on the mandrel;

tension reference means adapted to provide a signal proportional to andrepresentative of a desired, predetermined tension in the wire;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal proportional toand representative of a deviation in measured tension from desiredtension; and

servo correcting means connected to said error sensing means andoperable in response to said error signal for changing the rotationalvelocity of the supply spool during rotation of the winding head tomodify the wire tension in accordance with said error signal, wherebysaid servo means affects the rotational velocity of the supply spool tochange the wire tension in a sense tending to decrease the magnitude ofthe error signal.

3. In a high speed filament winding apparatus for winding filament abouta core, the apparatus having a rotatable winding head coaxial with thecore, a filament supply spool rotatably mounted concentric with therotating winding head and means for rotating the winding head atrelatively high rotational velocities for winding a helical coil aboutthe core, apparatus for maintaining a predetermined tension in thefilament during winding comprising:

tension sensing means coupled to the winding head and interposed in thepath of filament travel and adapted to provide a signal proportional toand representative of the tension in the filament being wound on thecore;

tension reference means adapted to provide a signal proportion-a1 to andrepresentative of a desired, predetermined tension in the filament;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an err-or signal proportional toand representative of a deviation in measured tension from desiredtension; and

servo correcting means connected to said error sensing means andoperable in response to said error signal for changing the rotationalvelocity of the supply spool relative to the rotational velocity of thewinding head to modify the filament tension in accordance with saiderror signal;

whereby a change in the rotational speed of said supply spool ohangesthe filament tension in a sense tending to decrease the magnitude of theerror signal.

4. In a high speed coil winding apparatus for winding resistance wireabout a mandrel, the apparatus having a rotatable Winding head coaxialwith the mandrel, a wire supply spool rotatably mounted concentric withthe rotating winding head and means for rotating the winding head atrelatively high rotational velocities for winding a helical coil aboutthe mandrel, apparatus for maintaining a predetermined tension in theresistance Wire during winding comprising:

tension sensing means coupled to the winding head and interposed in thepath of resistance wire travel and adapted to provide a signalproportional to and rep resentative of the tension in the resistancewire being wound on the mandrel;

tension reference means adapted to provide a signal proportional to andrepresentative of a desired, predetermined tension in the resistancewire; error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal proportional toand representative of a deviation in measured tension from desiredtension; and servo correcting means connected to said error sensingmeans and operable in response to said error signal for changing therotational velocity of the supply spool relative to the rotationalvelocity of the winding head to modify the resistance wire tension inaccordance with said error signal;

whereby a change in the rotational speed of said supply spool changesthe resistance wire tension in a sense tending to decrease the magnitudeof the error signal.

5. In a high speed filament winding apparatus for winding a filamentabout a core, the apparatus having a rotatable winding head coaxial withthe core, a filament supply spool rotatably mounted concentric with thewinding head and means for rotating the winding head at rel atively highrotational velocities for winding a helical coil on the core, apparatusfor maintaining a predetermined tension in the filament comprising:

tension sensing means including a cantilever beam coupled to the windinghead and interposed in the path of filament travel to be deflected inproportion to filament tension, deflection sensitive transducer meansmounted on said cantilever beam and adapted to provide a signalproportional to and representative of the tension in the filament beingwound on the core, and means for energizing said transducer means;

tension reference means adapted to provide a signal proportional to andrepresentative of said transducer means signal at a desired,predetermined tension in the filament;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal representing adeviation in measured tension from desired tension; and

servo means connected to said error sensing means and operable inresponse to said error signal for changing the rotational velocity ofthe supply spool relative to the rotational velocity of the winding headto modify the filament tension in accordance with said error signal,whereby said servo means, by changing the rotational speed of the supplyspool, changes the filament tension in a sense tending to decrease themagnitude of the error signal.

6. In a high speed coil winding apparatus for winding resistance wireabout a mandrel, the apparatus having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted concentric withthe winding head and means for rotating the winding head at relativelyhigh rotational velocities for winding a helical coil mandrel, apparatusfor maintaining a predetermined tension in the resistance wirecomprising:

tension sensing means including a centilever beam coupled to the windinghead and interposed in the path of resistance wire travel, strain gagemeans mounted on said cantilever beam and adapted to provide a signalproportional to and representative of the tension in the resistance wirebeing wound on the mandrel and means for energizing said strain gage;

tension reference means adapted to provide a signal proportional to andrepresentative of said strain gage signal at a desired, predeterminedtension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal representing adeviation in measured tension from desired tension; and

servo means connected to said error sensing means and operable inresponse to said error signal for changing the rotational velocity ofthe supply spool relative to the rotational velocity of the winding headto modify the resistance wire tension in accordance with said errorsignal, whereby said servo means, by changing the rotational speed ofthe supply spool, changes the wire tension in a sense tending todecrease the magnitude of the error signal.

7. In a high speed coil winding apparatus for winding resistance wireabout a mandrel, the apparatus having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted concentric withthe winding head and means for rotating the Winding head at relativelyhigh rotational velocities for winding a helical coil mandrel, apparatusfor maintaining a predetermined tension in the resistance wirecomprising:

tension sensing means including a cantilever beam coupled to the windinghead and interposed in the path of resistance wire travel, strain gagemeans mounted on said cantilever beam and adapted to provide a signalproportional to and representative of the tension in the resistance wirebeing wound on the mandrel and means for energizing said strain gage;

tension reference means adapted to provide a signal proportional to andrepresentative of said strain gage signal at a desired, predeterminedtension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means for providing an error signal representing adeviation in measured tension from desired tension; and

servo means connected to said error sensing means and operable inresponse to said error signal for changing the rotational velocity ofthe supply spool relative to the rotational velocity of the winding headto modify the resistance wire tension in accordance with said errorsignal, whereby said servo means affects the rotational speed of saidsupply spool to change the wire tension in a sense tending to decreasethe magnitude of the error signal.

8. In a high speed coil Winding apparatus for winding resistance wireabout a mandrel, the apparatus having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted on the windinghead and means for rotating said Winding head at relatively highvelocities for winding a helical coil on the mandrel, apparatus formaintaining a predetermined tension in the resistance wire comprising:

tension sensing means coupled to the winding head and interposed in thepath of resistance wire travel and adapted to provide a first signalproportional to and representative of the tension in the resistance wirebeing wound on the mandrel;

tension reference means adapted to provide a second signal proportionalto and representative of a said '12 first signal in response to adesired, predetermined tension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means and operable in response to applied first andsecond signals for generating an error signal having a magnitude andpolarity representing the deviation in measured tension from desiredtension; and

servo means connecting the supply spool and said error sensing means andoperable in response to said error signal for changing the rotationalvelocity of the supply spool by an amount related to the magnitude ofsaid error signal and in a direction related to the polarity of saiderror signal to modify the resistance wire tension, whereby said errorsignal changes the rotational speed of said supply spool to change thewire tension to correspond to the desired predetermined tension.

9. In a high speed coil winding apparatus for winding resistance wireabout a mandrel, the apparatus'having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted concentric withthe winding head, means for rotating the winding head at relative highrotational velocities for winding a helical coil on the mandrel, andmeans for feeding the mandrel at a preset speed in an axial direction,apparatus for maintaining a predetermined tension in the resistance wirecomprising: tension sensing means connected to the winding head andinterposed in the path of resistance wire travel, and including straingage means adapted to provide a first signal proportional to andrepresentative of the tension in the resistance wire being Wound on themandrel;

tension reference means including variable resistance means adapted toprovide a second signal proportional to and representative of the firstsignal produced by said strain gage means at a desired, predeterminedtension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means including potential source means forelectrically energizing said tension sensing and reference means forproviding an error signal in response to applied first and secondsignals, having a polarity and magnitude representing a deviation inmeasured tension from desired tension; and

servo means connected to said error sensing means and operable inresponse to said error signal having a first polarity for increasing therotational velocity of the supply spool relative to the rotationalvelocity of the winding head to decrease the resistance wire tension andoperable in response to said error signal having a second polarity fordecreasing the rotational velocity of the supply spool relative to therotational velocity of the winding head to increase the resistance wiretension, the magnitude of the increase and decrease being proportionalto the magnitude of the error signal, whereby said servo means affectsthe rotational speed of said supply spool to change the wire tension ina sense tending to decrease the magnitude of the error signal.

10. In a high speed coil winding apparatus for winding resistance wireabout a mandrel, the apparatu having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted on the windinghead and concentric therewith, and means for rotating the winding headat relatively high rotational velocities for winding a helical coil ofresistance wire on the mandrel, apparatus for maintaining apredetermined tension in the resistance wire comprising:

tenson sensing mean coupled to the winding head,

including strain gage means interposed in the path of resistance wiretravel and adapted to provide a first signal proportional to andrepresentative of the ten- 13 sion in the resistance wire being wound onthe mandrel;

tension reference means adapted to provide a second signal correspondingto the signal resulting from said strain gage means in response to adesired, predetermined tension in the resistance Wire; error sensingmeans coupled to said tension sensing means and said tension referencemeans and operable in response to first and second signals to generatean error signal having a polarity and magnitude respectivelycorresponding to the sense and magnitude of the difference betweenmeasured tension and desired tension; servo drive means connected tosaid error sensing means and operable in response to said error signalfor producing a rotational motion corresponding to a supply spoolvelocity increment suflicient to produce the desired predeterminedtension; and diiferental drive means having a first input coupled to themeans for rotating the Winding head, a second input coupled to saidservo drive means and an output coupled to apply rotational motion tothe supply spool, said output being equal to the sum of the appliedinputs, whereby said difierential drive means modify the rotationalspeed of the supply spool to change the wire tension in a magnitude anddirection tending to decrease the magnitude of the error signal derivedtherefrom. 11. In a high speed coil winding apparatus for windingresistance wire about a mandrel of non-uniform cross section, theapparatus having a rotatable Winding head coaxial with the mandrel, awire supply spool rotatably mounted on the winding head and concentrictherewith, and means for rotating the winding head at relatively highrotational velocities for winding a helical coil of resistance wire onthe mandrel, apparatus for maintaining a predetermined tension in theresistance Wire comprising:

tension sensing means coupled to the winding head, including strain gagemeans interposed in the path of resistance wire travel, and adapted toprovide a first signal proportional to and representative of the tensionin the resistance wire being wound on the mandrel;

tension reference means adapted to provide a second signal correspondingto the signal resulting from said strain gage means in response to adesired, predetermined tension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means and operable in response to first and secondsignals to generate an error signal having a polarity and magnituderespectively corresponding to the sense and magnitude of the diiferencebetween measured tension and desired tension;

servo drive means connected to said error sensing means and operable inresponse to said error signal for producing a rotational motioncorresponding to a supply spool velocity increment suflicient to producethe desired predetermined tension;

mandrel compensating means connected to the winding head rotating meansincluding apparatus for generating an output motion to compensate forthe nonuniformity of the mandrel cross section during each rotation ofthe winding head;

first differential drive means having a first input coupled to saidmandrel compensating means output motion, a second input coupled to saidservo drive means and an output; and

second difierential drive means having a first input coupled to themeans for rotating the winding head, a

second input coupled to said first differential drive means output andan output coupled to apply rotational motion to the supply spool, saidoutput being equal to the algebraic sum of all of the applied inputs,whereby said first and second differential drive means modify therotational speed of the supply spool to change the wire tension duringeach rotation of the winding head in a magnitude and direction tendingto decrease the magnitude of the error signal derived therefrom and tocorrect for the non-uniform shape of the mandrel.

12. In a high speed coil winding apparatus for winding resistance Wireabout a mandrel of non-uniform cross section cyclically varying in theaxial direction the apparatus having a rotatable winding head coaxialwith the mandrel, a wire supply spool rotatably mounted on the windinghead and concentric therewith, means for rotating the winding head atrelatively high rotational velocities for winding a helical coil ofresistance Wire on the mandrel, and means for axially advancing themandrel apparatus for maintaining a predetermined tension in theresistance Wire comprising:

tension sensing means coupled to the winding head,

including strain gage means interposed in the path of resistance wiretravel, and adapted to provide a first signal proportional to andrepresentative of the tension in the resistance wire being wound on themandrel;

tension reference means adapted to provide a second signal correspondingto the signal resulting from said strain gage means in response to adesired, predetermined tension in the resistance wire;

error sensing means coupled to said tension sensing means and saidtension reference means and operable in response to first and secondsignals to generate an error signal having a polarity and magnituderespectively corresponding to the sense and magnitude of the differencebetween measured tension and desired tension;

servo drive means connected t-o said error sensing means and operable inresponse to said error signal for producing a rotational motioncorresponding to a supply spool velocity increment sufi'icient toproduce the desired predetermined tension;

compensating and correcting means having a first input coupled to themeans for rotating the Winding head, a second input coupled to saidservo drive means, a third input coupled to the mandrel advancing meansand an output coupled to apply rotational motion to the supply spool,said ouput modifying the rotational speed of the supply spool duringeach rotation of the winding head to change the wire tension in amagnitude and direction tending to decrease the magnitude of the errorsignal derived therefrom to compensate for non-uniformitie in mandrelcross section and to modify and correct the compensation with axialmovement of the mandrel.

References Cited by the Examiner UNITED STATES PATENTS 2,334,880 11/1943Marlow 29-33 2,964,252 12/1960 Rosenberg 242-9 2,989,256 6/1961 Lee242-9 3,031,152 4/1962 Cohen et al 242-7551 3,105,179 9/1963 Young etal. 318-6 3,148,816 9/1964 Martin et a1. 226- 3,156,397 11/1964 Davies318-6 X FRANK J. COHEN, Primary Examiner. B. S. TAYLOR, Examiner.

1. IN A HIGH SPEED WINDING APPARATUS FOR WINDING A FILAMENT ABOUT ACORE, THE APPARATUS HAVING A WINDING HEAD ROTATABLE ABOUT THE CORE, AFILAMENT SUPPLY SPOOL ROTATABLY MOUNTED ON THE WINDING HEAD AND MEANSFOR ROTATING THE WINDING HEAD AT RELATIVELY HIGH ROTATIONAL VELOCITIESTO FORM A COIL ABOUT THE CORE, APPARTATUS FOR MAINTAINING APREDETERMINED TENSION IN THE FILAMENT COMPRISING: TENSION SENSING MEANSCOUPLED TO THE WINDING HEAD AND INTERPOSED IN THE PATH OF FILAMENTTRAVEL AND ADAPTED TO PROVIDE A SIGNAL PROPORTIONAL TO THEREPRESENTATIVE OF THE TENSION IN THE FILAMENT BEING WOUND ON THE CORE;TENSION REFERENCE MEANS ADAPTED TO PROVIDE A SIGNAL PROPORTIONAL TO ANDREPRESENTATIVE OF A DESIRED, PREDETERMINED TENSION IN THE FILAMENT;ERROR SENSING MEANS COUPLED TO SAID TENSION SENSING MEANS AND SAIDTENSION REFERENCE MEANS FOR PROVIDING AN ERROR SIGNAL PROPORTIONAL TOAND REPRESENTATIVE OF A DEVIATION IN MEASURED TENSION FROM DESIREDTENSION; AND SERVO CORRECTING MEANS CONNECTED TO SAID ERROR SENSINGMEANS AND OPERABLE IN RESPONSE TO SAID ERROR SIGNAL FOR CHANGING THEROTATIONAL VELOCITY OF THE SUPPLY SPOOL DURING ROTATION OF THE WINDINGHEAD TO MODIFY THE FILAMENT TENSION IN ACCORDANCE WITH SAID ERRORSIGNAL, WHEREBY SAID SERVO MEANS AFFECTS THE ROTATIONAL VELOCITY OF THESUPPLY SPOOL TO CHANGE THE FILAMENT TENSION IN A SENSE TENDING TODECREASE THE MAGNITUDE OF THE ERROS SIGNAL.